This invention relates to a composite seal structure as well as to a coupling arrangement employing the composite seal structure for a cannula. More particularly, this invention relates to a composite seal structure for use in the health care industry.
As is known, the health care industry is concerned with microorganisms such as bacteria and the like which may cause health problems. In some cases, people become patients because these microorganisms become unmanageable and threaten or endanger the health of the patient.
Patients requiring therapy are often placed in a position where their normal defenses against microorganisms are compromised. As a result, the patients may develop nosicomial infections while being treated for another disease during therapy. As has been recognized, a major cause of nosicomial infections has been due to connection/disconnection of tubing lines, especially in the area of IV therapy. This is one reason why most IV Administration Sets (IV tubing with connectors) are discarded every forty eight hours.
In some cases, patients have been provided with a shunt or catheter which has been placed in fluid flow communication with a vein, for example, in a wrist or in the hand so as to permit access to the vein from time-to-time, for example, for the injection of drugs, dialysis fluids and the like. In such cases, the shunts have usually been provided with a sealing membrane, such has a rubber septum, in order to prevent a flow from the vein as well as to seal the opening leading to the vein against microorganisms and the like. In order to pass a fluid through the shunt, use has been made of cannulae having sharp tips which are able to penetrate through the rubber septum and, thus, provide for flow communication with the interior of the shunt. Such cannalae can be subsequently removed with the rubber septum closing on itself to again form a seal. However, use of sharp-pointed cannulae creates certain problems. First, the rubber septum can be "cored" by the cannalae so that a core of material is removed from the rubber septum with possible passage into the shunt and thus into the patient. Also, repeated piercing of the rubber septum by sharp pointed cannulae can result in a permanent opening being formed through the rubber septum thereby defeating the purpose of the septum.
In order to avoid the problems presented by sharp-pointed cannulae, use has been made of blunt-ended cannulae, such as described in WO90/l2606 (International Application No. pCT/US90/01819). In such cases, the rubber septum has been provided with a slit through which a blunt-ended cannula may pass from time-to-time. However, such an arrangement requires a locking member in order to create a mechanically coupled unit between the blunt-ended cannula and an injection site which houses the rubber septum. In addition, the rubber septum requires mounting in a manner so as to be compressively deformed so as to create a dome-like shape and to provide for closing of the slit after removal of the cannula. Accordingly, the overall coupling arrangement between the cannula and the injection site is relatively complex and cumbersome to use. In addition, repeated piercing of the rubber septum over a period of time may result in some loss of elasticity in the rubber septum leading to a situation in which the slit may not be completely closed after removal of the cannula.